CCM counts the Cyclomatic Complexity of your whole project. This parameter allows to define how many occurrences you would like to see in the report. The occurrences with greatest Cyclomatic Complexity appear in the top of the list.

Then in case you define 5 as Number of metrics, it is going to bring you the 5 highest Cyclomatic Complexity occurrences in the source folder you specified.

Default value is 30 (same as CCM Add In for VS).